Page "Underground mining (hard rock)" Paragraph 16

* Point anchor bolts ( or expansion shell bolts ) are a common style of area ground support.

A point anchor bolt is a metal bar between 20 mm – 25 mm in diameter, and between 1 m – 4 m long ( the size is determined by the mine's engineering department ).

There is an expansion shell at the end of the bolt which is inserted into the hole.

As the bolt is tightened by the installation drill the expansion shell expands and the bolt tightens holding the rock together.

Mechanical bolts are considered temporary support as their lifespan is reduced by corrosion as they are not grouted.